This invention relates to a comb-shaped graft copolymer, (hereafter "comb" for brevity), to a process for making the comb, and to a polymer blend made with the comb. The comb is made by a free radical polymerization of an ethylenically unsaturated monomer with a macromolecular monomer ("macromer" for brevity) of a haloalkylene oxide ("HAO" for brevity) homopolymer, random or block copolymer. The comb copolymer and blends of the comb with a polymer(s) may be cured.
A process for making a comb of a macromer of polylactone with terminal acrylyl unsaturation and compatible blends thereof with another synthetic resinous material (referred to as a "matrix polymer") is disclosed in my U.S. Pat. No. 5,061,772; and blends of a comb copolymer of a macromer having pendant polylactone chains is disclosed in the aforementioned '944 application. I have now found that a comb with a terminal acrylyl or methacrylyl group or "head" and pendant polyether chains, which always include some HAO repeating units, may be made in an emulsion or suspension polymerization process analogous to that used to make the comb in my '772 patent; and, that it is only because an emulsion or suspension polymerization process provides a comb having adequately high molecular weight ("mol wt"), that I can successfully use the comb in the aforementioned blends. An acrylyl or methacrylyl head is referred to herein as a "(meth)acrylyl" head for convenience, and, as more fully described hereafter, is derived from an .alpha.,.beta.-monoolefinically unsaturated alcohol.
More specifically this invention relates to a process for making a comb by free radical polymerization of a macromer of a haloalkylene oxide, optionally in combination with another olefinically unsaturated monomer(s), the macromer having a single (meth)acrylyl head at one end, through which it (the macromer) is polymerizable, and a terminal hydroxyl (OH) group, or an end-capping group derived from the OH group at the other end. Each "tine" (pendant chain) of the comb is an uninterrupted one (that is, having no branch) having at least two repeating units derived from a HAO, preferably epichlorohydrin ("ECH"), with the tine terminating with a OH group, or an end-capping group derived from the OH group.
Macromers of polyether with terminal (meth)acrylyl unsaturation are disclosed in U.S. Pat. No. Re. 31,468 reissued Dec. 20, 1983, to Chin C. Hsu, the disclosure of which is incorporated by reference thereto as if fully set forth herein. Note that Hsu suggested copolymerizing his macromer but did not realize that, because it had a single terminal double bond he would get a comb copolymer. In view of the actual structure, corrected upon reissue, and several disclosures, for example in U.S. Pat. Nos. 4,302,558; 4,332,919; 4,315,081; 4,543,390; 4,604,414; and 4,699,964, relating to making comb copolymers with an acrylyl-headed macromer, particularly of ethylene oxide, it was evident that the Hsu macromer could yield a macromer if it could be made. Since both the Hsu macromer and the monomers used to provide the comb are water-insoluble, the copolymerization is typically run in solution in non-aqueous solvents. The result is a low mol wt comb copolymer having a number average molecular weight less than 100,000. It was therefore all the more surprising that an aqueous polymerization, whether in suspension or emulsion, would yield a comb copolymer of the Hsu macromer which comb would have a mol wt (Mn) greater than 100,000.
Analogous considerations apply to styryl terminated and allyl terminated macromers of polyethers taught in U.S. Pat. Nos. 4,680,358 and 4,722,978 issued July 1987 and February 1988 respectively to Simon Hsiao-Pao Yu. Neither of the macromers nor the monomers used to make the comb copolymers are water-soluble. Each macromer was made in non-aqueous solvents. Yet comb copolymers of each having a mol wt greater than 100,000 are made by suspension or emulsion polymerization.
A macromer, by definition, has only a single olefinic double bond. The macromers used to produce the comb copolymers are insoluble in water, as are the copolymers produced. The blend is of a known matrix polymer, typically one which is commercially available, and which may or may not be cocurable, with the comb chosen for the blend. The macromer may be of either acrylically, styrenically or allylically unsaturated polyether containing plural HAO repeating units, and, in each case the comb is formed with an ethylenically unsaturated monomer (simply "monomer" for brevity).
It is essential that the macromer used to prepare the comb contains at least two, and preferably several repeating units derived from a HAO, because, in addition to providing desirable mechanical compatibility with numerous matrix polymers in which the comb may be blended, halogen atoms in the pendant chains of the comb provide active sites through which the blend is cured. In the specific instance where a comb is made by copolymerizing butyl acrylate with a macromer of polyepichlorohydrin ("MPECH"), the pendant chains of polyepichlorohydrin ("PECH") allow the comb to be compatible with poly(vinyl chloride) (PVC) or chlorinated poly(vinyl chloride) (CPVC); and, the presence of the Cl atoms in the tines allows the comb to be co-cured (also sometimes referred to as being "covulcanized") when blended with a homopolymer or copolymer of a HAO such as epichlorohydrin ("ECH").
Polymerization of the (meth)acrylyl-headed macromer to form comb copolymers which are a special form of graft copolymers, differs from conventional graft copolymerization in the sequence of formation of the backbone relative to the formation of the graft unit.
Macromers used in this invention have a Mn in the range from about 300 to about 3000 though even higher mol wts up to about 10,000 may be used, if desired. The term macromer is used herein to denote a prepolymer made from at least one ring-opened HAO with a "(meth)acrylic" head group. If the macromer is formed from a single HAO it is referred to as a "homomacromer"; if from more than one comonomer which appears randomly, it is referred to as a "macromer copolymer"; and, if a copolymer is specifically formed by sequential copolymerization, it is referred to as a "macromer block copolyether".
The macromer is preferably formed by cationic ring-opening polymerization of at least one HAO in conjunction with a hydroxyalkyl (meth)acryate which functions as the generator of the propagating species, and a suitable cationic ring-opening catalyst. The hydroxyalkyl (meth)acrylate, for example, 2-hydroxyethyl acrylate or 2-hydroxyethyl methacrylate is referred to as the "propagator" because its function is to generate the OH group (which is the propagating species), in the presence of a cationic initiator. The macromer has substantially uniform mol wt distribution such that the ratio of the weight average mol wt (Mw) to the number average mol wt (Mn) is not substantially above about 3, preferably less than 2.
The (meth)acrylyl terminated macromer used in this invention is preferably made in a manner analogous to that described in my '358 and '978 patents except that one starts with an alcohol having a terminal (meth)acrylyl group. The (meth)acrylyl head of the alcohol does not undergo carbocationic polymerization under the acidic conditions required for the cationic ring-opening polymerization of the HAO used. The polymerization proceeds by polyaddition of the HAO to the OH group which is the propagating species.
The preferred (meth)acrylyl headed macromer used in the blend of this invention is formed by a process which comprises, polymerizing
(A) a cationically ring-openable cyclic ether selected from the group consisting of at lest one haloalkylene oxide, and optionally (i) an alkylene oxide having the structure ##STR1##
wherein, x is an integer in the range from 0 to about 4, except that when x&gt;1, a second alkylene oxide having x=1 or 0 must be present, and,
R.sup.1, R.sup.2 and R.sup.3 are independently selected from the group consisting of hydrogen, C.sub.1 -C.sub.20 alkyl (having from 1 to about 20 carbon atoms) and haloalkyl, and, at least one of R.sup.1, R.sup.2 and R.sup.3 is hydrogen; and, (ii) an aliphatic or aromatic glycidyl ether having the structure ##STR2##
wherein R.sup.4 represents a member selected from the group consisting of a substituted hydrocarbon group, i.e. C.sub.1 -C.sub.20 alkyl or substituted alkyl, particularly haloalkyl, alkoxyalkyl, aryl (Ar) or substituted aryl (Ar-Q) particularly wherein Q represents C.sub.1 -C.sub.10 alkyl or haloalkyl; and,
(B) a hydroxyalkyl acrylate represented by the structure ##STR3## wherein,
R.sup.5 is H or C1-C20 alkyl, preferably C1-C5 alkyl and most preferably CH.sub.3, and,
R.sup.6 is selected from a saturated group consisting of branched or linear alkylene, haloalkylene, alkoxyalkyl, haloalkoxyalkyl, each C.sub.1 -C.sub.20, aralkylene, haloaralkylene, aralkoxyl, and haloaralkoxy, each C.sub.7 -C.sub.20 ; in the presence of an effective amount of
(C) a cationic initiator selected from the group consisting of Friedl-Crafts acids, relatively strong protic organic and inorganic acids, oxonium salts and stable carbenium ions; so as to produce a water-insoluble macromer having the structure EQU R--(M).sub.m --OH (IV)
wherein R represents the residue of (A),
M represents a repeating unit of at least one haloalkylene oxide which is ring-opened and the HAO is present in an amount in the range from 50% to 100% in the macromer, and,
m represents an integer in the range from 2 to about 500, more preferably from 2 to about 300.
The preferred styryl-headed macromer used in the blend is formed in an analogous manner by using a styrylically unsaturated primary or secondary alcohol wherein the ethylenic unsaturation is adjacent to an aromatic ring, represented by the structure ##STR4##
The preferred allyl-headed macromer used in the blend is formed in an analogous manner by using an allylically unsaturated primary or secondary alcohol wherein the ethylenic unsaturation is adjacent to a saturated carbon atom, represented by the aliphatic structure ##STR5##
In a manner analogous to that described in my '358 and '978 patents, a macromer block copolyether may be prepared by polymerizing plural cyclic ethers sequentially, by using the macromer as a propagator, so as to have the structure EQU R--(M').sub.m' --b--(M").sub.m" --OH (VII)
wherein M' and M" represent two ring-opened cyclic ethers, and at least one is a HAO; and, m' and m" are integers each in the range from 1 to about 300 such that m'+m"=m.
The HAO is selected from the group consisting of a haloalkyl epoxide, haloalkaryl epoxide, haloalkyl glycidl ether, and haloalkaryl glycidyl ether. Preferred haloalkyl epoxides are epichlorohydrin, epibromohydrin, epiiodohydrin, epifluorohydrin, 3-chloro-1,2-epoxybutane, 3-chloro-2,3-epoxybutane, 3,3-dichloro-1,2-epoxypropane, and 3,3,3-trichloro-1,2-epoxypropane. A preferred haloalkaryl epoxide is chloromethylphenylene oxide. Preferred haloalkyl glycidyl ethers are 1,1-bis(chloromethyl)ethyl glycidyl ether, 2-chloroethyl glycidyl ether, 2-bromoethyl glycidyl ether, 2,2,2-trichloromethyl ethyl glycidyl ether. A preferred haloalkaryl glycidyl ether is chloromethyphenyl glycidyl ether. The most preferred HAO is epichlorohydrin.
The critical importance of having repeating units derived from a HAO in a pendant chain of copolymer of the macromer is that each of the chains provides active sites (Cl atoms) through which the chains may be cured or co-cured if desired. Another point of critical importance is that the pendant chains of the comb copolymer are compatible with many matrix polymers. The chains of the comb copolymer may be cured; or, a mixture of combs having active halogen sites may be co-cured; or, a comb may be co-cured with a polymer having active halogen sites such as a homopolymer or copolymer of ECH, of chlorinated polyethylene or of poly(chloroprene).
This invention relates to using the water-insoluble macromer, whether homomacromer, or, macromer of random or block copolyether, to prepare a comb copolymer of the macromer which either by itself, or more preferably, with a wide array of monomers, is used for the specific purpose of forming either a non-curable blend with a matrix polymer, or, a blend which is co-curable with a matrix polymer.
The properties of the comb, cured by itself, or not cured, may be tailored by choosing the polyether components of the macromer, the monomer with which the macromer is to be copolymerized to form the comb, and the ratio of the monomer to the macromer. Yet another degree of flexibility is obtained by curing a mixture of combs in which the pendant chains may be the same or different, and the comonomers used to form each of the combs may be the same or different.
The properties of an uncured blend of a comb with a matrix polymer, may be tailored by choosing the comb with a first set of desirable properties, and the matrix polymer with another set of desirable properties not possessed by the comb copolymer. Analogously, the cured blend of a comb with a matrix polymer is tailored by choosing a comb with a first set of desirable properties, and the matrix polymer with another set of desirable properties not possessed by the comb. It is thus possible to obtain a hybrid blend with the desirable properties of both the comb and the non-curable or co-curable polymer. The curing of the blend may take place after mixing, or during dynamic mixing.
Curing through the halogen atoms, especially chlorine atoms, is well known in the art. Most commonly the comb copolymer, by itself or as a blend, can be cured by a diamine, a thiourea, or an imidazole curing agent. Of thioureas available, ethylene thiourea is the most widely used. Of diamines available, hexamethylene diamine carbamate (Diak No. 1 from DuPont) and piperazine hexahydrate are the most widely used. Generally an acid acceptor, such as red lead or magnesium oxide, is required in the cure system. If desirable, plastiizers, lubricants, processing aids and stabilizers may also be included in the cure system.
More specifically, cured homopolymers and copolymers ECH, commercially available under the HYDRIN.RTM. trademark (of The B. F. Goodrich Company), are known to have excellent resistance to degradation by ozone, water and hydrocarbon fuels, particularly gasoline and jet fuel. These cured polymers also have excellent gas transmission resistance; a bladder of PECH filled with air, chlorine or methane under pressure, does not lose a significant amount of pressure even over a very long period provided the temperature is not raised above about 100.degree. C.
Cured acrylate homopolymers and copolymers, such as those sold under the HyTemp trademark (of The B. F. Goodrich Company) on the other hand, can easily withstand temperatures as high as about 200.degree. C. and are oil- and water-resistant, but have poor resistance to hydrocarbon fuels; they also have poor resistance to gas transmission.
By curing a blend of the comb copolymer (of acrylic monomer(s) and macromer of PECH) and PECH, a co-curable hybrid blend is obtained which has the desirable properties of both polymer components blended into it; and the degree to which the properties of the hybrid blend approach the properties of the hydrocarbon backbone or the polyether pendant chains can be adjusted by choosing the ratio of polyether units in the blend.
In the past, attempts made to co-cure blends of PECH and an acrylic elastomer met with limited success. See A. C. Fernandes et al J. Appl. Polym. Sci. 32, 6073 (1986) and C. Stanescu Kautsch. Grumm. Kunstat 32, 647 (1979). A blend of PECH with an epoxy-containing acrylic elastomer to improve co-curability is taught in U.S. Pat. No. 4,511,689.